The yield of agriculture crops may be reduced as a result of the hazard of weeds. In order to retrieve the loss of yield, a large amount of herbicides have to be applied to control the weeds each year. In recent year, agricultural crops confront increasing hazard from weeds. Moreover, the abuse of herbicides has increased the resistance of weeds against pesticides, leading to declined efficacy of weeds control year by year.
The traditional method of enhancing herbicidal activity and broadening herbicidal spectrum of existing herbicides is to mix two or more herbicidal substances with different herbicidal activity. If mix two or more herbicidal active chemicals, its herbicidal efficacy may be more prominent than applying a single herbicide. When the efficacy of a mixture with two or more ingredients exceeds the anticipated efficacy of each ingredient, it is called “synergistic effects”. However, only under certain circumstances, when two or more substances having herbicidal activity are mixed together, the herbicidal mixture exhibits synergistic effects. As a result of the difference in herbicidal efficacy, absorption rate, transmission and metabolism and so on, the herbicidal activity of most mixtures is lower than that of each ingredient when applied separately. The “Antagonistic Effects” has described such situation that when the efficacy of a mixture with two or more ingredients having herbicidal activity is lower than the anticipated efficacy of each ingredient when applied separately. The “Additive Effect” has described such situation that the herbicidal efficacy of mixture of two or more substances having herbicidal activity equals to the herbicidal efficacy of each ingredients applied separately.
Pyroxasulfone, with chemical name as 3-[5-(difluoromethoxy)-1-methyl-3-(trifluoromethyl) pyrazol-4-ylmethylsulfonyl]-4,5-dihydro-5,5-dimethyl-1,2-oxazole, is represented by the following chemical structure:

Pyroxasulfone was described in EP1364946 and US20050256004. Although Pyroxasulfone is a highly effective pre-emergence herbicide, its activity becomes low after the emergence. When Pyroxasulfone is applied to certain dicotyledonous crops, such as cotton, sunflower, soybean, and brassica crops, such as canola and oil rape and some gramineous crops, such as rice, wheat, rye and barley, the crops may suffer from unacceptable level of harms.
Thifensulfuron methyl, also named “Londax”, is represented by the following structure:

Thifensulfuron methyl is systemic conductive post-emergence selective herbicides, and an inhibitor of branched-chain amino acid synthesis, which is capable of inhibiting the biosynthesis of valine, leucine and isoleucine to prevent cell division, then stop sensitive crops from growing. It is mainly applied to control broadleaves weeds in the field of wheat, barley, oats, corn, such as redroot pigweed, purslane, descurainia sophia, capsella, salsola, catchweed bedstraw, speedwell and Malachium aquaticum (L.), while it is ineffective to thistle, bindweed and grass weeds. In general, the sensitive weeds stop growing after application and die after 1 week.
In the current, the herbicide spectrum is limited because of regulation to ensure the safety of crops. Application of a single herbicide is unable to completely and effectively control the weeds in the field of crops, on the other side, over-dosed herbicide or unevenly application is likely to produce unacceptable toxic to current crops or post-harvest crops. Pyroxasulfone is a highly effective herbicide used before emergence, but becomes less active after the emergence stage. Besides, the compatibility of Pyroxasulfone with some dicotyledonous crops, such as cotton, sunflower and beans, brassica crops, such as canola and oil rape, and certain gramineous crops, such as rice, wheat, rye and barley, is not ideal, as it not only damages the target plants, but also harms crops at unacceptable level. In principle, the damage to crops can be eased by decreasing the application rate, while its efficacy of control target plants also reduced accordingly.